1. Field of the Invention
This invention relates generally to 2-halopyrimidine derivatives represented by the general formula (I), ##SPC2##
wherein R.sup.2 represents hydrogen, halogen, particularly chlorine, bromine, iodine and fluorine, C.sub.1 -C.sub.6 lower alkyl, aryl, particularly phenyl, C.sub.1 -C.sub.6 alkyl substituted phenyl, halogen substituted phenyl or the like, or an amino group, particularly NH.sub.2, NR.sup.5 H or NR.sub.2.sup.5 wherein R.sup.5 is similar to R.sup.2 and R.sup.4 represents a C.sub.1 -C.sub.6 lower alkyl, and X represents a halogen, particularly chlorine, fluorine, bromine, and iodine, and further relates to novel intermediate compounds useful for their preparation. The compounds represented by the formula (I) are important for use in the preparation of sulfa drugs, purine bases or the like.
2. Description of the Prior Art
Heretofore, only one method has been known for the production of 2-halogeno-4-alkoxy-6-aminopyrimidine derivatives represented by the general formula (I). In that method, 6-amino-2,4-dichloro-pyrimidine derivatives are reacted with sodium alcoholate (refer to Chemical & Pharmaceutical Bulletin vol. 13, page 557 (1965) and Japanese Patent publication number 19804/1966). However, as described in those reports, the major product is 2-alkoxy-4-chloro-6-aminopyrimidine, although 4-alkoxy-2-chloro derivative is obtained as a by-product in a poor yield, because the reactivity of the halogen atom at the 2-position of the pyrimidine ring is far superior to the reactivity of the halogen atom at the 4-position of the pyrimidine ring. It is therefore chemically impossible to obtain 2-halogeno-4-alkoxy-6-aminopyrimidine derivatives as a main product by the prior art technique. Moreover, the prior art technique suffers certain other disadvantages. For one, it requires a procedure which is undesirable from a pollution point of view. For another, phosphorous acid salts are produced from the phosphorous oxychloride which amplifies the pollution difficulties. The prior art technique is therefore industrially not completely satisfactory.